Nonlinear discrete-time models: state-space vs. I/O representations

This paper compares state-space and input–output realizations for nonlinear discrete-time dynamic models. For linear models, these two realizations are essentially equivalent and their structures are closely related, but these statements do not hold for nonlinear models. We illustrate this point with simple, realistic examples for which only one of the two realizations exists or for which both exist but their structures are profoundly different. Overall, the main point of this paper is the importance of the choice of realization in the development of nonlinear dynamic models.     

土酸溶液中溴化十六烷基吡啶对锌的缓蚀作用及吸附热力学研究

用失重法研究了土酸溶液中溴化十六烷基吡啶对锌的缓蚀作用，发现溴化十六烷基吡啶在锌表面上的吸附是产生缓蚀作用的重要原因，且吸附规律服从Langmuir吸附等温式。用Sekine方法处理实验数据，从而获得了吸附过程△H^0、△S^0和△G^0等一系列重要热力学参数。     

Study of (3-mercaptopropyl)trimethoxysilane reactivity on zinc: Comparison with organothiol and organosilane thin films

To assess the reactivity of both terminal functions of the (3-mercaptopropyl)trimethoxysilane molecule, three types of zinc substrate (mechanically polished, electrochemically reduced and electrochemically oxidized) were modified concurrently by 1H,1H,2H,2H-perfluorooctyl-triethoxysilane and 1H,1H,2H,2H-perfluorooctanethiol. Surface characterization has been carried out with X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy and contact angle measurements. Classical electrochemical techniques were employed to investigate corrosion inhibition of zinc along with thin films grafting. It is found that electrochemical oxidation enhances the grafting of the -Si(OCH₃)₃ groups while electrochemical reduction facilitates the formation of thiolate bonds, leading both to modified surfaces of much better quality compared to modified polished zinc samples.     

Corrosion Condition Evaluation at Muddy Creek Bridge

Corrosion rates were measured at the exposed spots of rebars near three corners of Muddy Creek Bridge located in northern West Virginia using a 3LP device. Also, chloride contents of the concrete samples taken from the vicinity of the spots were analyzed using a wet chemical method that had been developed in this study. The average corrosion rate over the three spots was 4.66 mA/m2, which is in the range of corrosion damage possible in 10–15 years. The average chloride content of the concrete over the three spots was 703 parts per million (ppm), which is well above the threshold limit value of 260 ppm. Although the corrosion rate measurement method using a 3LP device is by manual operation, it is found to be reliable and effective, and, thus, recommended for future studies of this kind of research. The wet chemical method developed in this study is found to be effective.     

Behavioral depression during cocaine withdrawal is associated with decreased spontaneous activity of ventral tegmental area dopamine neurons.

Withdrawal from an escalating-dose, bingelike regimen of cocaine administration in rats produced significantly depressed levels of locomotor activity during the nocturnal portion of the day-night cycle. This effect was observed during the first 48 hrs of testing. Extracellular single-unit recordings of ventral tegmental area (VTA) dopamine (DA) neurons revealed no differences between saline- and cocaine-treated rats with respect to basal firing rates. However, significantly fewer spontaneously active VTA DA neurons were encountered in rats withdrawn from binge cocaine. As with the nocturnal hypoactivity, this effect was observed only during the first 48 hrs of withdrawal. These findings suggest that short-term DA neuron dysfunction during cocaine withdrawal temporally corresponds to behavioral disruptions that are similar to those described in human addicts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strategic appraisal of energy models for Mozambique

The needs that an energy supply system must meet are constantly changing, due to technological, social and political reasons. Effective energy planning is a dynamic process that is repeated periodically and adjusts to changing conditions. Energy decision makers and planners are no longer able to rely on inductive decision making since they have to investigate the effect of various decision parameters and possible future changes. To help in this process, models have been developed where estimates of future load growth, candidate power plants, fuels and other key factors can be introduced, from which the planners can evaluate decision parameters and the available alternatives. The paper presents the different methodologies and practices that are used by 11 energy models for energy demand forecasting, supply side management and generation expansion planning, demand side management and integrated resource planning. The paper concludes to the presentation of a strategic appraisal of the examined energy models appropriate for energy planning in Mozambique. Three models are proposed for conducting demand forecasting, generation expansion planning and demand side management. Copyright © 2002 John Wiley & Sons, Ltd.     

Roles for Psychologists in End-of-Life Care: Emerging Models of Practice.

Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Economic Model to Optimize Underground Utility Protection

The need for better protecting our vital infrastructure from being damaged or destroyed has received increased attention since the terrorist attacks on September 11, 2001. The tragedy of having thousands of innocent people die before the eyes of an entire nation awakened people to the reality of “managed” attacks of unthinkable magnitudes. However, tragedies of a smaller scale are a daily occurrence but accepted as “collateral damage” of work in an unsafe environment. This paper presents a cost-benefit analysis to address the question of how much money should be spent in protecting underground utilities from damage. During the study of an actual incident it was found that the total costs of such accidents are vastly underreported because only costs for emergency responses and repair are tallied up. This paper makes the case that a comprehensive approach for assessing the total economic impact of such incidents on the public, business, and government is the critical stepping stone to a mathematical optimization of expenditure for damage prevention. In addition, the reader will quickly realize that the use of the presented optimization model provides theoretical underpinning for the engineering profession in its effort to better protect our critical infrastructure from terrorist attacks.     

Reasoning, Integration, Inference Alteration, and Text Comprehension.

This paper reports how the study of formal logical reasoning provides insight into more everyday types of reasoning, such as that involved in language comprehension. Both of these types of cognition are thought to involve the use of mental models, and so it is reasonable to think that the cognitive operations needed for formal logical reasoning would be involved in everyday reasoning as well. We focused on three aspects of formal reasoning: (a) the integration of information into a common mental model, (b) the drawing of inferences, and (c) the coordination of alternative possibilities. We were able to show that the integration and inference components were related to narrative comprehension processes, but the coordination of alternative models was not. Thus, there is evidence for some overlap in the mental processes used in formal and everyday reasoning. This further justifies the study of formal logical reasoning as a window into certain types of everyday reasoning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corrosion of tin in citric acid solution and the effect of some inorganic anions

The corrosion behaviour of tin in different concentrations of citric acid solutions (0.3–1.0 M, pH=1.8) was studied at 30 °C by potentiodynamic technique. The E/I profiles exhibit an active passive behaviour. The active dissolution involves one anodic peak A associated with a dissolution of the metals as Sn(II) species. The passivity is due to the formation of thin film of SnO₂ and or Sn(OH)₄ on the anode surface. The cathodic sweep shows a small peak C related to the reduction of the passive film. The peak current density I_p of peak A increases with increasing both acid concentration and sweep rate.

The effects of adding increasing concentrations of Na₂CrO₄, NaMoO₄, NaNO₃ and NaNO₂ on the corrosion of tin in 0.5 M citric acid at 30 °C were investigated. Both CrO₄²⁻ and MoO₄²⁻ ions inhibit the corrosion of tin and the extent of inhibition enhances with their concentrations. Addition of either NO₃⁻ or NO₂⁻ accelerates the corrosion of tin. NO₃⁻ ions are more aggressive than NO₂⁻ ions.